地铁车站PBA洞桩法施工力学效应研究

Study on Mechanical Effect of PBA Method in Metro Station

以新疆地铁一号线王家梁站为工程背景,建立车站-地层计算模型,应用FLAC3D软件模拟洞桩法施工,对地层位移变化、塑性区分布及重要围护结构受力进行研究,并优化导洞施工方案。分析表明:导洞开挖与扣拱施工是引起地表沉降的两个主要阶段,二者引起地表沉降比例高达近90%,导洞与车站拱顶超前注浆加固非常有必要;已有现场测量数据与数值计算结果吻合度较高,验证了模拟结果的正确性,基于此对后续施工引起地表沉降值做出预测;洞桩法施工对周围地层造成多次扰动,但扰动范围较小,中柱是主要的受力结构,施工中应重点监测;通过对比分析,确立了先中后边、先上后下的最优导洞开挖方案。

Based on the engineering background of Wangjialiang subway station of Xinjiang Metro Line 1,the station-strata calculation model was established. The displacement of the surrounding strata,the distribution of plastic zone and the force of important envelope were studied by FLAC3D software. Besides,the scheme of pilot tunnel excavation was optimized. The study showed that the pilot tunnel excavation and the arching are two main stages which result in the total subsidence,and the proportion of the ground subsidence can reach up to nearly 90%. It is necessary to strengthen the soil with grouting scheme up the pilot tunnel and the arch. The numerical result is in good agreement with the numerical simulation result,so the correctness of the numerical result is verified. Based on the numerical result,the surface subsidence induced by subsequent construction is predicted. The construction of PBA( pile-beamarch) method has caused repetitious disturbances to surrounding strata,but the disturbance range is small. The middle pile is the main force structure,and it should be monitored more frequently; By comparison,the best construction plan of pilot tunnel excavation is determined. In horizontal plane,the method with inside pilot tunnel construction followed by outside one is more effective than other way in controlling surface settlement. In vertical plane,the method with upper pilot tunnel construction followed by lower one is more effective than the other way in controlling surface settlement.